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11.
Polyurethanes were prepared from toluene diisocyanate (TDI), 1-4-butane diol (BDO) and polycaprolactone-based triols with varying molecular weights. Among each molecular weight triol-based urethane, hard segment content was varied from 20% to 70%. Differential scanning calorimetry, tensile testing, and Iosipescu shear testing were done on all the various urethanes prepared. Thermal characterization data revealed the dependence of phase separation on hard segment content as well as on the triol molecular weight. Tensile data and Iosipescu shear data further confirmed the observations made from the DSC data. The data further indicated that phase separation can greatly improve the modulus of cross-linked segmented urethanes. Adhesion of these urethanes to glass surface was evaluated using soda-lime float glass plate. Urethane samples were cast on the air side of the glass plates and adhesion was measured in shear mode. Adhesion data indicated that in addition to hard segment content, modulus, cross-link density, and molecular weight of the triols, phase separation seems to be a major factor in controlling adhesion. Surfaces of the failed adhesion samples were also analyzed and the failure mode was found to be cohesive, in varying degree, with the different urethane systems. 相似文献
12.
Influence of Grain Size on Ferroelastic Toughening and Piezoelectric Behavior of Lead Zirconate Titanate 总被引:1,自引:0,他引:1
Lead zirconate titanate specimens, at composition Zr48.9+- 1.0 / Ti51.1+-1.0 of grain sizes ranging from 0.5 to 15 (μm were prepared by hot pressing. The fracture toughness showed a 40% increase in the fine-grained specimens. Poling produced anisotropy in the fracture toughness. A tensor representation for the fracture toughness, now a function of the crack plane normal and the poling direction, is developed. The maximum and minimum values in the toughness tensor are shown to be related to the unpoled toughness by a simple phenomenological relationship. We also find that the piezoelectric coefficient, d33 , shows a slight increase for the fine-grained specimens, which is in conflict with the general view that smaller-grained materials can sustain vanishingly small values of spontaneous polarization. 相似文献
13.
Influence of Distributed Particle Size on the Determination of the Parabolic Rate Constant for Oxidation by the Powder Method 总被引:1,自引:0,他引:1
The established analysis for the study of oxidation using powder specimens is based on the assumption of monosized particles. The experiments, however, are conducted on powders with a distributed particle size. Here we present a statistical approach for the calculation of the rate constant for oxidation. The results of the analysis are applied to new data on oxidation studies of dense powders of silicon carbonitride amorphous ceramics. The monosized model requires a wide range of values for the rate constant to fit the short term and the long-term data, leading to considerable ambiguity in the estimate of the parabolic rate constant, k p , for oxidation. In contrast the statistical model fits over the entire range of data, yielding a much more reliable value for k p . For example, the monosized approach gave a value in the range 19.7 × 10−18 < k p < 2.7 × 10−18 m2 /s. In contrast, the statistical model yields a specific value of 4.5 × 10−18 m2 /s. 相似文献
14.
Alok Singh Sitaram Dash Mohammed Kamruddin Puthupparampil K. Ajikumar Ashok K. Tyagi Vinjamoor S. Raghunathan Baldev Raj 《Journal of the American Ceramic Society》2002,85(4):927-932
Formation of nanocrystalline calcia from calcite has been studied in situ via transmission electron microscopy. The crystallographic transformation occurred via two mechanisms: the first is by distortion of the cleaved rhombohedron of calcite, formed by {104} planes in hexagonal coordinates, into a cube. This produced a microstructure of oriented, elongated nanocrystals of calcia with planar boundaries. In the second mechanism, the micrometer-sized parent calcite particles broke up into nano-sized grains as the decomposition began, leading to irregularly shaped, randomly oriented nanocrystals of calcia. 相似文献
15.
Chlorendic anhydride based polyester ( I ,) tetrachlorophthalic anhydride based polyester ( II ), dibromoneopentyl glycol based polyester ( III ,) general purpose polyester ( IV ,) blend of dibromoneopentyl glycol based polyester with general purpose polyester ( V ,) chlorendic anhydride and dibromoneopentyl glycol based polyester ( VI ), and a blend of chlorendic anhydride based polyester and dibromoneopentyl glycol based polyester ( VII ) were prepared and their chemical resistance and moisture absorption studied in various reagents, acid, alkali, and water, at 25 and 65°C. It is found that the polyester ( III ) is the least affected in the presence of the acids. In 20% NaOH, there was a decrease in weight for all polyesters at both the temperatures compared to the control except the polyester ( VII ). Increase in weight of all the polyesters was observed during the absorption of moisture both at 25 and 65°C. The increase was higher at higher temperature. Polyester ( III ) thus shows the least absorption of moisture. 相似文献
16.
M. Sharan Chandran K. Padmanabhan D. K. Dipin Raj Yashasvi Chebiyyam 《Journal of Adhesion Science and Technology》2020,34(5):511-530
AbstractInterfacial adhesion of composite materials plays an important role in their mechanical properties and performance. In the present investigation, analysis of the interfacial properties of self-reinforced polyamide composites by using microbond multiple fibre pull-out test is emphasised. Microbond specimens prepared through thermal processing are tested for their interfacial properties by multiple fibre bundle pull-out tests and compared with that of traditional single fibre pull-out test specimens. Multiple fibre pull-out addresses the volume fraction as well as eliminates the possibility of fibre breakage before matrix shear. Higher scatter in the data in the samples is addressed in the present studies. FTIR and Fractographic studies are carried out for deep understanding of the post pull-out interfacial adhesion. 相似文献
17.
Amanda Baker Michael Lanagan Clive Randall Elena Semouchkina George Semouchkin Khalid Z. Rajab Richard Eitel Khalid Z. Rajab Raj Mittra Sorah Rhee Peter Geggier Claus Duschl Günter Fuhr 《International Journal of Applied Ceramic Technology》2005,2(6):514-520
At the Keck Smart Materials Integration Laboratory at Penn State University, low-temperature co-fired ceramic (LTCC) material systems have been used to fabricate a number of devices for a variety of applications. This article presents an overview of the integration of the concepts and materials that we have used to achieve miniaturization and unique device function. Examples of microwave filters, metamaterial antennas, and a dielectrophoretic cell sorter will be presented, with emphasis on device modeling and design, prototype construction methods, and test results. 相似文献
18.
Harsh Bhasin Gitanshu Behal Nimish Aggarwal Raj Kumar Saini Shivani Choudhary 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2016,20(9):3403-3410
Diploid genetic algorithms (DGAs) promise robustness as against simple genetic algorithms which only work towards optimization. Moreover, these algorithms outperform others in dynamic environments. The work examines the theoretical aspect of the concept by examining the existing literature. The present work takes the example of dynamic TSP to compare greedy approach, genetic algorithms and DGAs. The work also implements a greedy genetic approach for the problem. In the experiments carried out, the three variants of dominance were implemented and 115 runs proved the point that none of them outperforms the other. 相似文献
19.
Design of Barrages with Genetic Algorithm Based Embedded Simulation Optimization Approach 总被引:2,自引:2,他引:0
Raj Mohan Singh 《Water Resources Management》2011,25(2):409-429
Barrages are hydraulic structures constructed across rivers to divert flow into irrigation canals or power generation channels.
The most of these structures are founded on permeable foundation. The optimum cost of these structures is nonlinear function
of factors that cause the seepage forces under the structure. There is, however, no procedure to ascertain the basic barrage
parameters such as depth of sheet piles or cutoffs and the length and thickness of floor in a cost–effective manner. In this
paper, a nonlinear optimization formulation (NLOF), which consists of an objective function of minimizing total cost, is solved
using genetic algorithm (GA). The mathematical model that represents the subsurface flow is embedded in the NLOF. The applicability
of the approach has been illustrated with a typical example of barrage profile. The results obtained in this study shows drastic
cost savings when the proposed NLOF is solved using GA than that of using classical optimization technique and conventional
method. A parametric analysis has also been performed to study the effect of varying soil and hydrological conditions on design
parameters and on over all cost. 相似文献
20.
This special issue showcases articles written from five of the best presentations at the Hot Chips 19 conference, held in August 2007. The guest editors give highlights of the conference and introduce the articles, which cover the mobile-optimized northbridge of AMD's Griffin microprocessor family; the IBM z10 next-generation mainframe microprocessor; fault tolerance in IBM's Power6 microprocessor; NVIDIA's Tesla unified graphics and computing architecture; and SiBEAM's 4-Gbps 1080p-capable uncompressed HD A/V wireless 60-GHz transceiver chipset. 相似文献